Centrosome dysfunction is the leading cause of microcephaly and is also associated with sterility, ciliopathy, and cancer. As the microtubule organizing centers of most eukaryotic cells, centrosomes build the bipolar mitotic spindle that segregates the duplicated genome into two daughter cells during cell division. In addition, centrosomes orchestrate numerous critical tasks during interphase, such as cell polarization, ciliogenesis, cell migration, and intracellular trafficking. The proposed research seeks to uncover novel paradigms of centrosome regulation. The results from this work are likely to fundamentally reshape current models of how centrosome activity is controlled in healthy and diseased cells. While most centrosome studies focus on maturation, the recruitment of proteins to the centrosome at mitotic onset, how centrosomes are regulated during interphase is little understood. In Aim 1, I will determine how centrosome function is regulated during interphase by Pericentrin-like-protein. Further, I propose to investigate the unknown roles of mRNAs that were previously localized to centrosomes. Many of these transcripts encode regulators of centrosome activity. In Aim 2, I propose to visualize mRNAs that localize to centrosomes and to investigate RNA localization mechanisms. I hypothesize that mRNA localization is an efficient strategy to quickly and locally control centrosome activity. To test this hypothesis, I will elucidte the mechanism and function of mRNA localization to centrosomes in Aim 3. Investigating these unexplored paradigms of centrosome regulation is essential to understand how centrosome function is modulated throughout the cell cycle and deregulated in disease. The NHLBI K22 Career Transition Award will provide mentored research and career development training to support the successful completion of the proposed research and to facilitate my transition to career independence. This award proposal was developed to leverage my experience in mRNA localization with my current training in centrosome biology. As part of a comprehensive career development plan, the mentored phase will include hands-on instruction, formal workshops, mentoring opportunities, and science communication activities. New technical skills to be learned include fluorescence recovery after photobleaching, super resolution microscopy, cell culture, and CRISPR genome editing. To address deficiencies in these areas and to provide tailored career preparation, the mentors and expert members of an advisory committee, comprising both intramural and extramural investigators, will provide frequent discussion, feedback, and evaluation. With this information in hand, I will launch my independent career as a principal investigator. Findings from the proposed research will form the basis of an NIH R01 funding application. Further, the completion of the proposed work will provide a more comprehensive understanding of how centrosome activity is regulated, aspects of which may be deregulated in a disease setting.